The present application is generally related to direct current (DC) electrical machines, such as DC motors, and particularly to systems that use such machines, for example, electric power steering (EPS) systems.
In control systems, such as an EPS, a state observer is a system or module that provides an estimate of the internal state of the real control system, from measurements of the input and output of the real system. Knowing the internal system state facilitates addressing technical problems associated with the real system; for example, stabilizing the real system using state feedback. Typically, the physical internal system state of the EPS cannot be determined by direct measurement. Instead, indirect effects of the internal state are observed by way of the system outputs. The state observer module in such cases facilitates reconstructing at least a part of the internal system state based on the output measurements.
For example, an EPS system includes a motor that facilitates providing a driver assist during operation of the EPS system. Motor velocity is a critical signal for control of the EPS system. The motor velocity may be directly measured using sensors and/or tachometers. However, such direct measurement requires additional hardware, which leads to additional costs as well as engineering. Accordingly, it is desirable to use a state observer module to estimate the motor velocity signal in addition to other aspects of the working of the EPS system, without significant loss of accuracy.